A one-liner is a computer program or expression (programming) that takes no more than a single line. In practice, one-liners will be entered and executed directly from the command-line. Perl is an excellent language to use when creating one-liners.

Many one-liners are practical. For example, the following Perl one-liner will reverse all the bytes in a file:

perl -0777e print scalar reverse filename

One-liners are also used to show off the differential expressive power of programming languages. Frequently, one-liners are used to demonstrate programming ability. Contests are often held to see who can create the most exceptional one-liner.

The following example is a C program (a winning entry in the Best one-liner category of the IOCCC.)

main(int c,char**v){return!m(v[1],v[2]);}m(char*s,char*t){return*t-42*s63==*t|*s==*t&&m(s+1,t+1):!*t:m(s,t+1)||*s&&m(s+1,t);}

This one-liner program is a glob pattern matcher. It understands the glob characters `* meaning `zero or more characters and ` meaning exactly one character, just like your unix shell.

Run it with two args, the string and the glob pattern. The exit status is 0 (shell true) when the pattern matches, 1 otherwise. The glob pattern must match the whole string, so you may want to use * at the beginning and end of the pattern if you are looking for something in the middle. Examples:

$ prog foo f ; echo $ $ prog best short program st*o**p* ; echo $

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